Machine for cutting screw threads



A. CHRISTEN MACHINE FOR CUTTING SCREW fl-IREADS Feb. 9, 1954 3 Sheets-Sheet 2 Filed Dec. 28, 1949 INVENTUR A DRE Cum STEN 11A, :N-MJ ATTORNEYS Feb. 9, 1954 A. CHRISTEN 2,668,303 MACHINE FOR CUTTING SCREW THREADS Filed Dec. 28, 1949 s Sheets-Sheet 5 INVENTUR ANDRE CHRISTE N BY wmwom LM'HL 6' PM ATTORNEYS Patented Feb. 9, 1954 UNITED S TATES PATENT OFF 1 CE MACHINE FOR CUTTING SCREW THREADS Andre Christen, Limeil-Brevannes, France Application December 28, 1949; Serial No. 135,374 Claims pri ri sc pplication France March 8... 1.949

The present invention relates to machine; for cutting the threads of screws having at least two crossed threads, a right hand one and a. left hand one, as it. the case with the screws or threaded shafts of automatic screw drivers, drilling devices, etcr (including a driving member having a reciprocating movement. on the screw, which causes. it to: rotate alwaysv in the same direction, one of the threads being used during the stroke in one direc- The tools are, of course, suitably inclined atv an angle. which is preferably adjustable, and they are sufiiciently distant from each other to permit of shifting the contact with bar 4 from one tool. to the other by a suitable transverse displacement of carriage 6.

I30 obtain the desired respective displacements of carriages 3 and 6., I make. use for instance of the. following means.

tion and the other during the returnstrokeh 10 The reciprocating motion of carriage 3 is con- Itschief. object is to provide a machine of this trolled by a drum 1 provided with helical ridges kind which is simpler than those used upto the 8, 3 on which runs. a. roller I carried by carriage present; time. 3. this drum being, driven with a speed suitably Preferred embodiments of the. present invenchosen with respect to that of. shaft 4, through tion. will be hereinafter described. with reference 15 means; including gears H, i2, for interconnecting to. the accompanying drawings, given merely by said shaft and said drum (it is supposed on the way of example and in which; drawing that energy is transmitted to shaft 4 Eigsnl and 2 show, respectively in elevationand through a belt 13. and a pulley [4). in plan. View, the. essential elements of a cutting The. speed ratio will be determined in particumachine for making right and left hand threads, 20 lar in such manner as to make it possible for each according to my invention.

Figs. 3 to are perspective views showing some of the elements of said machine- Figs. 3a; 4a, 5a diagrammatically illustrate; the positions of the cutting tools on Figs. 3,. 4: and 5.

The machine includes a carriage system. hold.- ing at least two tools intended. to work alternately on the shaft to be threaded, this system being driven with a reciprocating motion. along: said shaft, itself rotated in a continuous: fashion.

It is found that, in these. conditions, one of the tools will cut a right hand (or left hand, according to the direction of rotation). thread during the stroke of the tool holder in one. direction, and

tool to out two or several threads of the same direction,

On the other hand, I provide, to control the reciprocating transverse motion of carriage 6,. a

device which actuates a finger l5 cooperating with a. notch t6 provided. in said carriage, movement being transmitted tothe finger through a grooved shaft ll (Figs. 3 to 5)).

This device includes, for instance, a cam I8 of suitable. shape driven together with drum 1, 8,

9; and intended to cooperate with various intermediate. levers such as 1.9, 20,. 2|, which will be more explicitly referred to hereinafter. Cam I8 includes two portions A and; B which correspond the other tool a left hand (or right hand) thread 33 respectively to the. two working positions (Figs. during the return stroke. 3c; and 4c) of tools; is, 2 andv two smaller inter- If, furthermore, I manage so that, atthebeginmediate portions G which correspond to a, stroke ning of a new cycle, the bar isnot located exactly end neutral position (Fig, an. in the same position as at the beginning of the The speed otrevolution oi shaft; 22: which can preceding one but, for instance, has rotated 49 ties-cam tll 'rssuchthat the twoportionsc correthroughone halfof a revolution or a smaller spend tothe two ends of the stroke of carriage 3. fraction of a revolution, each of the tools can out In orderto permit. of obtaining a gradual intwo or more right hand threads and twoor more crease of the depth of cut of said tools, I make left hand threads. use of a roller or other intermediate member 23 Such an operation can be. obtained, for ininterposedbecweentwo levers. suchas I9, this stance, as illustrated by the drawings.

Figs. land 2 show tools I and, 2. located opposite each other are carried by a double carriage including: on the one hand, a primary carriage 3 having a reciprocating motion along the shaft 4 to be machined, said carriage being, for thispurpose, mounted slidable on rods. 5;. and on-the other hand, a secondary carriage B movable transversely to the first one and carrying tools I and 2, by means of tool holders of conventional type.

roller being movable in. such manner that the ratio between the movements transmitted by cam 18 and the movements received by finger I 5 varies for every reciprocation of the holder.

Of course, the automatic depth of cut. increase should, be the same for both tools, which. will be obtained. if, in the neutral, position of carriage 6, as shown by Fig. 5, the surfaces of levers i9 and 20 that cooperate with roller 23 are parallel.

In order to displace roller 23, I have recourse to any known system used in machine tools, for instance to a cam 24 capable of cooperating with the finger 25 of a lever 26 acting on roller 23.

Cam 24 is for instance driven by a pawl 21 cooperating with a ratchet wheel 28, rigid with said cam 24, pawl 21 being operated by the displacements of a lever 29 rigid with arm IS. A retaining pawl is visible at 30. Cam 24 is, for instance, in the form of an Archimedean spiral.

The system is advantageously completed by means for automatically stopping the machine when the depth of cut of the threads has reached a given value, at the end of a revolution of cam 24, these means including, for instance, if the machine is driven by an electric motor, a switch 3| controlled at 32 by cam 24 by means of an abutment 33 carried by said cam.

Figs. 3 to show the machin in three different positions, Figs. 3 and 4 corresponding to the action of the respective tools and Fig. 5 corresponding to the end of a carriage stroke.

Such a 'machine permits of establishing, in a very simple manner, threaded rods with crossed threads, as diagrammatically shown on the drawing at 34.

Of course this machine might be used for other purposes, in particular for cutting threads in only one direction, one of the tools remaining inactive.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and efiicient embodiments of my invention,

it should be well understood that I do not wish to be limited thereto as there might be changes mad in the arrangement, disposition and form of the parts without departing from the prin- 5 ciple of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

1. A machine for cutting crossed threads in a cylindrical bar which comprises, in combination, a frame including bearing means for said bar, a carriage movable with respect to said frame in a direction parallel to the axis of said bar, a drum journalled in said frame parallel to said bar, means for driving said bar and said drum each constantly in the sam direction, cooperating cam. and follower means on said drum and said carriage for imparting a reciprocating movement to said carriage parallel to said bar in response to rotation of said drum always in the same direction, two tools mounted on said carriage movable with respect thereto only transversely to said direction and arranged for cutting threads in said bar in opposite directions, respectively, cam means having opposed working surfaces and operatively connected with said driving means and means actuated by said working surfaces for actuating said tools transversely to said carriage alternately in one direction and the other in response to successive reversals of the movement thereof to bring said tools alternately into working contact with said bar during opposed displacements of said carriage along said bar, respectively.

2. A machine for cutting crossed threads in a cylindrical bar which comprises, in combination, a frame including bearing means for said bar, a

carriage movable with respect to said frame in a direction parallel to the axis of said bar, a drum journalled in said frame parallel to said bar, means for driving said bar and said drum each constantly in the same direction, cooperating cam and follower means on said drum and said carriage for imparting a reciprocating movement to said carriage parallel to said bar in response to rotation of said drum always in the same direction, two tools mounted opposite to each other on said carriage movable with respect thereto only transversely to said direction, said tools being inclined in opposite directions with respect to said bar for cutting threads therein during opposed displacements of said carriage, respectively, cam means having opposed working surfaces and operatively connected with said driving means and means actuated by said working surfaces for actuating both of said tools simultaneously transversely to said carriage alternately in one direction and the other in response to successive reversals of the movement thereof, to bring said tools into working contact with said bar during opposed displacements of said carriage along said bar respectively.

' 3. A machine for cutting threads in a cylindrical bar which comprises, in combination, a frame including bearing means for said bar, a first carriage movable with respect to said frame in a direction parallel to the axis of said bar, a drum journalled in said frame parallel to said bar, means for drivin said bar and said drum each constantly in the same direction, cooperating cam and follower means on said drum and said carriage for imparting a reciprocating movement to said carriage parallel to said bar in response to rotation of said drum always in the same direction, a second carriage slidably carried by the first one in a direction transverse to the first mentioned direction, two tools mounted opposite to each other on said second carriage, said tools being inclined in opposite directions with respect to said bar so as to be able to cut threads therein during opposed displacements of said first carriage, respectively, cam means having opposed working surfaces and operatively connected with said driving means and means actuated by said Working surfaces for reciprocating said second carriage with respect to the first one n response to successive reversals of the movement of said first carriage to bring said tools alternately into working contact with said bar during opposed displacements of said first carriage along said bar respectively.

4. A machine according to claim 1 further including cam means operative by said bar and drum driving means for increasing the depth of out of said tools for successive cutting operations thereof.

5. A machine according to claim 3 further including cam means for gradually increasing the amplitude of the transverse reciprocating movement of said second carriage and pawl and ratchet means operative by said second carriage reciprocating means for actuating said cam means on every successive cutting operation of each of said tools.

ANDRE CHRISTEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 908,146 Schlesinger Dec. 29, 1908 1,866,838 Brustle July 12, 1932 2,468,478 Ardoin Apr. 26, 1949 FOREIGN PATENTS Number Country Date 108,497 Great Britain Aug. 16, 1917 

